[1] : Jargon File (4.3.1, 29 Jun 2001)

mode bit n. common a flag, usually in hardware, that selects
   between two usually quite different modes of operation. the
   connotations are different from flag bit in that mode bits are mainly
   written during a boot or set-up phase, are seldom explicitly read, and
   seldom change over the lifetime of an ordinary program. the classic
   example was the ebcdic-vs.-ascii bit 12 of the program status word of
   the ibm 360.


see also:
flag 

[2] : The Free On-line Dictionary of Computing (27 SEP 03)

mode bit
     
        a flag, usually in hardware, that selects between two
        usually quite different modes of operation.  the
        connotations are different from flag bit in that mode bits
        are mainly written during a boot or set-up phase, are seldom
        explicitly read, and seldom change over the lifetime of an
        ordinary program.  the classic example was the
        ebcdic-vs.-ascii bit 12 of the program status word of the
        ibm 360.  another was the bit on a pdp-12 that controlled
        whether it ran the pdp-8 or the linc instruction set.
     
        jargon file
     
     
see also:
flag ibm 360 jargon file 

Addressing Mode >> A Words
Addressing Mode, definition of term: Addressing Mode
addressing+mode_pag1.html

A La Mode >> A Words
A La Mode, definition of term: A La Mode
a+la+mode_pag1.html